Dimethyl titanium dichloride



United States Patent Ofiice 3,021,349 Patented Feb. 13, 1962 3,021,349 DIMETHYL TITANIUM DICHLORIDE Edward H. de Butts, Wilmington, DeL, assignor to Hercules Powder Company, Wilmington, Del., :2 corporation of Delaware No Drawing. Filed Dec. 29, 1959, Ser. No. 862,474 3 Claims. (Cl. 260-4295) This invention relates to the preparation of organotitanium compounds and, more particularly, to the preparation of dimethyl titanium dichloride.

In accordance with the present invention, it has been found that dimethyl titanium dichloride is produced in a useful form by contacting titanium tetrachloride or methyl titanium trichloride with bis(cyclopentadienyl) dimethyl titanium.

Methyl titanium trichloride is produced by the reaction of titanium tetrachloride with one-half of an equimolecular amount of bis(cyclopentadienyl) dimethyl titanium at a temperature in the range of about 80 C. to about C. and dimethyl titanium dichloride is produced by reaction of methyl titanium tn'chloride with one-half of an equimolecular amount of bis(cyclopentadienyl) dimethyl titanium at a temperature in the same low range.

Bis(cyclopentadienyl) dimethyl titanium, which has been made available by the process of Piper and Wilkinson, J. Inorg. and Nuclear Chemistry, 3, 108 (1956), has been found to be a particularly useful alkylating reagent for these reactions.

When bis(cyclopentadienyl) dimethyl titanium is reacted in greater than one-half equimolecular amounts with titanium tetrachloride, it is possible to produce dimethyl titanium dichloride in a one-step reaction. When the ratio of titanium tetrachloride to bis(cyclopentadienyl) dimethyl titanium is between 2:1 and 1:1, a mixture of dimethyl titanium dichloride and methyl titanium trichloride is produced. When the ratio of titanium tetrachloride to bis(cyclopentadienyl) dimethyl titanium is less than 1:1, the product is substantially all dimethyl titanium dichloride.

If desired, the methyl titanium trichloride may be prepared separately by reaction of titanium tetrachloride with a metal alkyl such as lithium alkyl, or aluminum alkyl provided that the reaction is carried out at a temperature sufliciently low that reduction of the titanium tetrachloride to titanium trichloride, which normally occurs at room temperature or above, does not take place. Generally, a temperature of below about 0 C. is required to form the methyl titanium trichloride in this reaction and preferably a temperature of 30 C. to -60 C. or less is used.

Since the organotitanium compounds are sensitive to oxygen, active hydrogen compounds, and water, the reactions involved are carried out under anhydrous conditions and in an inert atmosphere.

The process of this invention is preferably carried out in an organic diluent which is inert under the reaction conditions. Such diluents include the hydrocarbons saturated with respect to olefinic and acetylenic unsaturation, e.g., methane, ethane, propane, butanes, hexanes, heptanes, octanes, cyclohexane, methyl cyclopentane, benzene, toluene, xylenes, cumene, cymene, and the hydrogenated analogs of these aromatic hydrocarbons. The diluents which may also be used are the halogenated hydrocarbons, e.g., chloromethane, dichloromethane, chloroform, carbon tetrachloride, dichlorodifluoromethane, ethylene chloride, acetylene tetrachloride, chlorofluoroethanes, chlorobenzene, chlorinated toluene and similar halogenated hydrocarbons.

The amount of diluent in the process is not critical and is sufiicient to produce a fluid reaction mixture.

When desired to produce the dimethyl titanium dichloride in situ for use in polymerization, the process is carried out in the presence of the olefin to be polymerized and its prior isolation is not necessary. When desired to produce the dimethyl titanium dichloride in a purified form, the process is carried out in the absence of unsaturated hydrocarbons.

The dimethyl titanium dichloride may be freed of excess titanium halide by recrystallization of the dimethyl titanium dichloride from inert solvent such as aliphatic, alicyclic, or aromatic solvents boiling in the range from about -20 C. to about 250 C. such as butane, pentane, octane, cyclohexane, methyl cyclopentane, benzene, toluene, xylenes, cymene, cumene, or halogenated derivatives of these solvents such as methylene chloride, chloroform, and chlorobenzene, for example.

The dimethyltitanium dichloride can be further purified by distillation or sublimation in high vacuum at temperatures from to 25 C.

The following examples illustrate the methods of this invention for carrying out the reactions involved. All parts and percentages are by weight.

EXAMPLE 1 Preparation of methyltitanium trichlaride Five parts of bis(cyclopentadienyl) dimethyl titanium were dissolved in parts of a purified anhydrous toluene. After cooling the solution to 80 C., 9.5 parts of titanium tetrachloride were added as a 1.0 molar solution in pentane with agitation. The mixture was then warmed to 0 C. and agitated at that temperature for 4 hours. The volatile components were then removed by distillation under high vacuum at 10 C. The excess titanium tetrachloride and solvent were then removed from this distillate by fractionally distilling at 36 C. under high vacuum. The methyltitanium trichloride in the residue was dissolved by means of pentane. Analysis of an aliquot of this solution showed it to contain 0.52 millimole of titanium per gram and 1.60 millimoles of chlorine per gram or a 3:1 ratio of chlorine to titanium; theoretical value is 3.

EXAMPLE 2 Preparation of dimethyl titanium dichloride A solution of 5.6 parts of methyl titanium trichloride in pentane was added to a solution of 5.7 parts of his- (cyclopentadienyl) dimethyl titanium in pentane at 40 C. The reaction mixture was allowed to warm to 0 C. and was agitated at that temperature for about 16 hours. It was then fractionally distilled at 0.2 mm. Hg. A first fraction taken at -36 C. to 0 C. was essentially solvent. The second fraction collected at 0 C. to 25 C. consisted of blackish purple crystals. These were dissolved and recrystallized twice from n-heptane. On analysis they were found to have a chlorine to titanium ratio of 2.0 (theory is 2.0)

EXAMPLE 3 To 10 moles of titanium tetrachloride in hexane solution was slowely added a solution of 20 moles bis(cyclopentadienyl) dimethyl titanium in hexane at -80 C. The solution was allowed to warm up to 0 C. and was then cooled again to 80 C. Black crystals of dimethyl titanium dichloride precipitated. These were separated by filtration and further purified by crystallization from hexane by dissolution at 0 C. followed by crystallization at 80 C. The crystals were distillable at 25 C. at 0.2 mm. pressure.

The compound prepared according to this invention is a violet to black substance, when in the solid state, and is sensitive to air, water, light, heat and halogens and dissolves in aliphatic and aromatic hydrocarbons and chlorinated hydrocarbon solvents to form a yellow solution.

to 30 'C, temperature range; This catalystis particu larly usefulin producing polymers of high viscosity and may be used as a pure catalyst orin combination with methyl titanium trichloride. Such a combination can be produced as a mixture in the process of this invention by regulating the amount of bis(cyclopentadienyl) dimethyl titanium used as the alkylating reagent. A particularly adyantageous characteristicof the present invention is" the limitation of the'replacement of the halogens on the titanium halide reagent to two by the bis(cyclopentadienyl) dimethyl titahium. i

application is a continuation-in-part of application Ser. No. 625,243, filed November 30, 1956, which discloses the preparation of the dimethyl titanium dichloride and methyl titanium trichloride in catalytically active form by reaction of"bistcyclopentadienyl) dimethyl titanium with titanium tetrachloride and the use thereof as catalysts in the polymerization of olefins.

What I claim and desire to protect by Letters Patent is:

1. The method of producing dimethyl titanium dichloride which comprises reacting a material of the group consisting of titanium tetrachloride and methyl titanium trichloride with bis(cyclopentadienyl) dimethyl titanium at a temperature in the range of C. to 0 C.

2. The method of producing dimethyl titanium dichloride which comprises reacting titanium tetrachloride with less thanan equimolecular amount of bis(cyclopentadienyl) dimethyl titanium at. atemperature in the range of. 80 C.v to 0 C;, separatingtmethyl titanium trichloride so produced and reacting the methyl titanium trichloride witha further amount of bis(cyclopentadienyl) dimethyl titanium at a temperature in the range of 80 C. to 0 C. and separating dimethyl titanium dichloride.

3. The method of producing dimethyl titanium dichloride in admixture with methyl titanium trichloridewhich comprises reacting titanium tetrachloride with bis(cyclo pentadienyl) dimethyl titanium in a molecular ratio of between about 2:1 and about 1:1 at a temperature in therange of 80 C; to-O C. 7'

UNITED I STATES PATENTS Brown et al Dec. 31, 1957 Kozikowski Dec. 8, 1959 

1. THE METHOD OF PRODUCING DIMETHYL TITANIUM DICHLORIDE WHICH COMPRISES REACTING A MATERIAL OF THE GROUP CONSISTING OF TITANIUM TETCHLORIDE AND METHYL TITANIUM TRICHLORIDE WITH BIS(CLOPENTADIENYL) DIMETHYL TITANIUM AT A TEMPERATURE IN THE RANGE OF -80* C. TO 0* C. 